Background: General transcription factor 3C polypeptide 4 (GTF3C4/TFIIIC90) is a subunit of the TFIIIC DNA-binding factor required for transcription of tRNA and 5S rRNA genes by RNA polymerase III. Human TFIIIC is composed of six subunits: TFIIIC220, TFIIIC110, TFIIIC102, TFIIIC90 and TFIIIC63, and TFIIIC35. GTF3C4/TFIIIC90 is required for RNA polymerase III transcription and interacts with TFIIIC220, TFIIIC110, TFCIIIC63, TFIIIB90, and RPC39. GTF3C4/TFIIIC90 has been shown to possess acetyltransferase activity specific for histone H3.